Riverine environments are stressed and damaged by anthropogenic actions, with chemical contamination a key factor, identified as potentially adversely impacting the aquatic network. Standardised Organisation for Economic Co-Operation and Development (OECD) tests are used to establish biodegradation rates of chemicals in the environment, however these tests are conducted in unrealistic conditions deficient of environmental realism. Increasing the environmental realism of OECD tests has the capacity improve prediction of chemical persistence and identify potential for damage to the environment. Moreover, the interactions between bedform, microbial biofilm communities and chemical biodegradation at the sediment-water interface are not considered in OECD tests. The current project explored the effects of bed-form characteristics on biofilm development and the consequences of sediment on biodegradation at the sediment-water interface. Novel flume systems were designed, constructed and used to develop methodologies to investigate the impact of bed form on hyporheic exchange. River water and sediment were sampled from a stretch of the River Dene (Wellesbourne, UK) and used as microbial inocula in chemical biodegradation studies using a series of specially designed re-circulating flume systems and ex-situ bottle experiments. Flume experimentation quantified the rate of microbial community development, topographical location and effective depth penetration on sediment beds within artificial watercourses, whilst simultaneously identifying the impact that this biofilm development possessed on hyporheic exchange. The effects of light and inoculum source on para-nitrophenol (PNP) biodegradation were also determined following OECD regulatory test protocols in an attempt to evaluate the realism of chemical biodegradation tests. Experimental data showed that microbial development varied on different sediment bed profiles, and that biofilms significantly reduced the rate of hyporheic exchange on small (0.5 mm), but not large (2.0 mm) sediment particle size bed materials. Additionally, this study found that light inhibited PNP degradation in all tests and that sediment sieving utilised in OECD tests decreased rates of biodegradation of PNP. This project revealed the importance of microbial biofilms in determining hyporheic exchange. However, further experimental work is recommended to investigate hyporheic exchange in heterogeneous sediments, whilst developing more inclusive approaches for chemical risk management by Regulatory bodies.